Although the causes remain unclear, data on childhood disability suggest that the proportion of children experiencing disability is steadily increasing, and that the conditions underlying those disabilities are shifting from a dominant mix of traditional medical conditions and orthopedic impairments to a preponderance of mental, behavioral, and developmental conditions. Questions remain about how much of this increase in prevalence is "real" and what proportion results from changes in recognition, diagnosis, availability of health care services, and the way that disability in children is measured. Nonetheless a large, and potentially growing, number of children are limited in their ability to engage in age-appropriate activities and face reduced opportunities to participate in social and educational offerings. These children are likely to become adults with chronic and disabling health conditions; as such they represent not only a burden for families, schools, and other institutions but also an enormous loss of human capital, with implications for ongoing health care, their economic well-being, and social welfare. The data presented here suggest a continuing challenge to the nation's public health system. Yet, clear data are lacking on the nature of the causes, consequences, and costs of disability.

There is obviously a need for better information, more complete data, and more up-to-date, comprehensive, and integrated measurement. Currently there exists a host of different surveys and data collection mechanisms that use different concepts, definitions, and measures. The resulting data are difficult to interpret, cross-link, and harmonize. These survey data sets also provide very little information about the causes, dynamics, trajectories, and burdens of disability, making it very difficult to develop effective prevention, intervention, or accommodation strategies. The Federal Interagency Forum on Child and Family Statistics, the National Academy of Science, or some similar neutral and cross-cutting organization should develop a plan to correct the deficiencies in the national data infrastructure and ensure that clear, complete, and comprehensive data on childhood disabilities are available to address key policy questions, including trends in prevalence, changing distributions, and long-term consequences of childhood disability.

Several major changes are occurring in the health care system and in health measurement that are likely to influence future trends in the prevalence and impact of disabilities on U.S. children. First, as health systems incorporate forward-looking programs designed to optimize the health of all citizens, the measurement of positive health development and health potential is becoming ever more important. For example, the inclusion of new measures of healthy development in the 2011 National Survey of Children's Health will provide additional opportunities to understand the factors that are associated with more optimal outcomes for children, including those with disabilities. Ultimately, better measures should result in a greater emphasis on connecting the dots across the life course, thus enhancing understanding of mechanisms that determine how at-risk families, toxic environments, and other social factors literally get under the skin, influence genetic predispositions and the development of biobehavioral pathways, and also produce resilience in the face of adversity.

One of the great opportunities to better understand the prevalence, determinants, and trends of childhood disability is the National Children's Study (NCS), sponsored by the Eunice K. Shriver National Institute for Child Health and Human Development. When fully implemented, this study will follow at least 100,000 children across the United States from preconception through the first twenty years of life. This study holds the promise of being able to measure many of the risk, protective, and promoting factors associated with a range of child outcomes, including those associated with the development of a range of impairments. The design of the NCS and its focus on multiple levels of dynamic interaction between children and their environment will also permit a more finely tuned analysis of how impairment manifests and the factors that influence differing levels of participation in normal daily activities.

Given the enormous investment in the NCS, and its potential capacity to address many (but not all) of the current information and data gaps, steps should be taken to consider linking the NCS measurement development process with other existing and ongoing data monitoring efforts. Such coordination could ensure greater harmonization of data elements and greatly improve the ability to cross-link data on health and disability in the future. While it is tempting to make the NCS the "great data hope" of the future, much can be done to make better use of existing data, including finding ways to upgrade periodic national health surveys with better and more explanatory questions about childhood disability, as well as linking health and education surveys with other program administrative data from special education, early intervention, and disability treatment programs. As the nation builds an electronic health information infrastructure, there will also be growing opportunities to collect new and different information on child health and disability and to take advantage of the power of electronic health records to better link data. This effort will not happen on its own, however, and requires a strategic design, leadership, and financial support.